1. Field of the Invention
The present invention relates to a semiconductor manufacturing process and in particular to a method of modifying conductive wiring.
2. Description of the Related Art
As the number of devices that may be included on a single semiconductor chip increases, the size of the device is reduced and the thickness of the photoresist layer is also reduced. Otherwise, light cannot reach the bottom of the thick photoresist layer during photolithography, such that the desired patterns cannot be precisely transferred on to the semiconductor substrate. Thus, a hard mask comprised of poly-silicon is proposed to replace the photoresist layer. The thickness of the hard mask can be greatly reduced for new generation manufacturing processes, to as little as 0.11 μm or less.
However, it is difficult to remove the poly-silicon hard mask in the plug formation process. Conventionally, a barrier comprising TiN/Ti is usually formed between the semiconductor substrate and the poly-silicon hard mask. In order to enhance the conductivity between the barrier and the substrate, a thermal treatment is usually performed, wherein the TiN/Ti barrier and the silicon substrate react with each other to form a highly conductive silicide. There is however, also a silicide formed between the poly-silicon hard mask and the TiN/Ti barrier. As a result, the silicide between the poly-silicon hard mask and the TiN/Ti barrier is difficult to remove by chemical mechanical polishing.